United Nations aid agencies say there's been an alarming deterioration in the situation in southern Sudan, with some seven hundred thousand people now at risk of famine as a result of crop failure and civil war.

A BBC correspondent who's just visited the worst-affected area, Bahr el-Ghazal, says desperately hungry Sudanese are on the move, looking for wild plants to eat.

The Sudanese government, which has curbed aid operations in rebel-held areas, has now allowed a second UN plane to airlift food to the region.

But our correspondent says this concession from the government may have come too late to stave off a terrible catastrophe.